[gunapologist99]

One of the things that helped Southwest dominate in the short-haul space, particularly in the Texas Triangle, was optimizing "turn-time" with a target of less than 10 minutes to both deplane and board passengers (10 minutes!)[0]

I wonder how lengthy charge cycles will affect the viability of fast turn times, especially for the short-haul segments that they're targeting for these new airliners. It seems like they'll need to either have extremely fast charging or be prepared for significant downtime between flights; where will the planes be stored while they're charging?

It's important to both invest in and appear to be investing in the future, but even a soft commitment of 100 planes seems like quite a bit, especially in the very competitive and cost-focused short-haul space.

0. https://www.npr.org/2015/06/28/418147961/the-man-who-saved-s...

[tadfisher]

Battery swaps could be viable, barring some complications in gate infrastructure and airframe design. Obviously this would be impossible if airframe designers incorporate battery cells in structural members, as some suggest to offset the weight penalty.

[Tossrock]

I've said for a while that electric planes are the perfect use case for aluminum-air batteries. Aluminum-air batteries have up to 8x the energy density of lithium ion, but are not rechargeable, so using them only makes sense if you have a system to recycle the used batteries. This doesn't make a ton of sense with cars, because cars are constantly going from random place to random place, and having to include a stop at a battery recycling center every ~1000km or whatever would be impractical.

But planes go between very limited sets of known points, with huge amounts of infrastructure. Adding in the capability to do Al-air battery swaps / recycling would be easy, and the benefits for the use case (huge weight savings, faster turnaround times by swapping vs charging) are big.

[EastLondonCoder]

Apparently Eviation is looking into aluminium air batteries https://en.wikipedia.org/wiki/Eviation_Alice

[throwawayboise]

Small tertiary airports often served by short regional flights don't have a lot of infrastructure. They have a couple of fuel trucks and a gate agent/security screener/baggage handler who might all be the same person.

[ars]

So instead of a fuel truck you have a battery swapper.

You'll have to ship the batteries somewhere they can charge/reprocess, but you also need to ship fuel, so it's a 1-to-1 tradeoff (you can ship the batteries by land).

[throwawayboise]

Is it 1:1? There are a lot more KWh in a tanker truckload of jet fuel than in the same volume of batteries.

[Tossrock]

Not that much more (theoretically) - Al-air batteries could reach up to ~8kWh/kg, which is in the same range as jet fuel's 12ish. Aluminum is also denser than jet fuel, so per unit volume it could be even closer.

[otterley]

What's the process for recycling an aluminum-air battery? And is it cost/energy effective to do so?

(If you think about it, closed-loop recycling of energy storage is just another form of recharging, but with extra steps.)

[Infernal]

From wikipedia[0] "it is possible to mechanically recharge the battery with new aluminium anodes made from recycling the hydrated aluminium oxide". I've found a few papers regarding recovery of aluminum from aluminum oxides, but I don't have the background to interpret them with an eye towards that process's impact on the overall efficiency of the battery.

[0] https://en.wikipedia.org/wiki/Aluminium–air_battery

[throwawayboise]

Production of aluminum metal from aluminum oxide is hugely energy-intensive. Aluminum plants often have an on-site utility-size power plant to provide the electricity. Is this same energy needed to recycle the oxide from the batteries? If so it seems like a non-starter, maybe unless it could be done with solar generation.

[ars]

> Is this same energy needed to recycle the oxide from the batteries?

The energy delivered by the battery in flight, is what you need to use to restore it back to fresh. The more energy you need the better your battery.

Why does it need to be specifically solar? Use electric from the grid, and as the entire grid changes over to other power sources so will this.

[mapt]

There is no "recharging" an aluminum-air battery, you add the energy back through recycling (smelting) it.

One of the big synergies is with renewables: With the right industrial process, you can treat this smelting process as a way to dump excess energy in peak production times.

[Hypx_]

It's the same idea of green hydrogen. Only hydrogen allows you to use pipelines instead of physically hauling everything. You also don't have to worry about the battery physically gaining weight as you fly.

[ComputerGuru]

I remember 20 years back, hydrogen was going to be it. There were prototype cars manufactured, calls for hydrogen fueling stations to be built, everyone scrambling to get on the hydrogen train. Then it all just fizzled out. It was probably one of the promised techs I most wish had lived up to the hype.

[otterley]

Doesn't smelting generate a ton of waste heat, though? Sounds like a process that uses far more energy than the aluminum-air battery can hold.

[Hypx_]

Because aluminum-air batteries are not rechargeable, they're fundamentally inferior to hydrogen fuel cells (which work in nearly the same way!). At least with hydrogen you can refuel the airplanes with a liquid instead of having to use a physical battery swap. Also, even higher energy density that doesn't gain weight during flight.

[nielsbot]

The "more info" page on their website says they are ruling out battery swaps, at least for now, since a battery swap would require a mechanical certification every time it was done.

They are swappable though: they explain that used battery packs can be replaced and that used packs can be used for a second purpose with less stringent requirements. For example, an energy storage facility at the airport.

[hutzlibu]

"Obviously this would be impossible if airframe designers incorporate battery cells in structural members, as some suggest to offset the weight penalty."

Why not do both?

Swap one part and charge just the internal batteries. But internal batteries does not sound so clever with limited lifetime anyway.

[tgsovlerkhgsel]

Charging is limited by two factors:

- the power you can get from the charger to the batteries - the power the cells can accept

You can reasonably easily fix the first point with custom infrastructure, so the second point will be the limiting factor, and that one means that it always takes e.g. 20 minutes to charge your batteries, regardless how many you're charging (because with a bigger battery, you're simply charging more cells in parallel, at the same speed per cell).

[justaguy88]

I've always wondered about this, do electric cars charge each cell in parallel? or are there some series connections?

[ehnto]

That's part of what made high speed rail so compelling. When done well you can be on the train, sat down and moving in just a few minutes. No airport security, long ticketing lines, baggage check-ins or fuss at the gate. Just walk in, bags in the overhead, sit down and away you go.

[darkwizard42]

I think high speed rail is compelling because of the speed and accessibility (which if built right -- looking at Japan) becomes an easy option for commute and transport between cities that is vastly more accessible than airports (Narita airport is FAR from Tokyo central)

The security check in, long ticket lines, etc. are all byproducts of security theater that has come through and honestly in the US, with TSA Pre, I'm pretty sure I spend more time sitting at the gate than ANY other process (check in, 5 min, security, 5 min, walking to gate, 5 min, sitting at gate waiting for boarding, 40 min)

100% agree that the ability to walk straight into a train, find your seat through multiple doors (even the wrong car) feels pretty good.

[tommi]

Well said though to clarify the reason why you wait 40 minutes at the gate is probably because you have to calculate some extra per each step leading to it. You can't be sure you'll make it in 5 minutes per check in, security and walk to the gate. Also, the added cost in time and money of missing a plane is quite high compared to missing a train e.g. in Europe, so that further increases the buffer you add to the process.

[NotSammyHagar]

I've been reluctant to get precheck because I hate to give up my fingerprints. There have been a few infamous mistakes where they messed up like the Oregon lawyer thought to be involved with the Spanish train bombers. Being in software, I know many immigrants to the us and they all have precheck and the border check version - while me and many of my natural born citizens don't have it, at least partly for that reason of fingerprints. I solved that problem for now by not flying during covid ;-) Am I unnecessarily paranoid? Probably.

[justaguy88]

Applying for a US work visa or residency involves writing down so much about yourself (inc. getting fingerprints), that pre-check afterwards feels like just re-providing a subset of the same paperwork

[darkwizard42]

Yeah this is a good point... I definitely don't want to miss my flight and now I have a really good and predictable handle on how long security and check in takes, but I never seem to have a good handle on how boarding will go (I usually just abide by the "domestic gates never close till 30 min before the flight earliest" rule)

[lifeisstillgood]

With all due respect, if they had built airports in the middle of cities, we would all be complaining about why we had to take a taxi to the train station miles from the city centre.

The big advantage of the train is being on the property ladder 100 years early.

[Symbiote]

Most cities that had relatively central airports have closed them (due to noise and pollution) and built new ones further out.

Cities continue to build new railway stations and lines, usually underground, to improve access to the centre.

[lifeisstillgood]

ok so my conjecture: an electric VTOL aircraft will mean cities rebuild airports. Of course it means Kitty Pride will be flying a Electric VTOL ...

But this will free up enormous tracts of land - the railways don't just use land for stations, but the railtrack takes up most of the land (in long strips as it were).

Imagine cities in 50 years, with rail land reclaimed, with Tokyo-like laws that prevent on-street parking (a valuable gift to car owners), freer flowing traffic, more walkable neighbourhoods. There is a lot to unpick.

[ehnto]

I think you're overstating how impactful railway land usage is, in total amount it's definitely a lot but per suburb or area it's not much and it more or less sits next to the rest of the suburb rather than dominating it. It provides far more value than an airport in my opinion. I can walk out my door and 5 minutes on to a train then into the city, there's no way to get a plane from my house to the city.

What you really want to reclaim I feel is roads from cars, we devote insane amounts of land to cars, car parking, and car travel..

The city of Adelaide is an interesting example if you're interested, it's a young city and built an airport 4km from the CBD, which means the CBD can't have tall buildings, the airport has a curfew, noise is a constant hot topic, and it takes up more land than our CBD and most prized suburbs do. It's likely sitting on hundreds of millions worth of real estate, while the train station takes up less than a city block and then the rails weave their way through the rest of suburbia. The most recent Southern Interchange, a car highway interchange, takes up more land than the train station does including it's convergence and junction yard, and all it does is connect two roads together.

The city also tore up all it's rail network when cars took over, and now it can't afford to put the rail back in now that it's proven to be the more sustainable and pragmatic option.

[lifeisstillgood]

>>> there's no way to get a plane from my house to the city.

I think I was drinking too much coffee.

But railway is just another road. In fact i suspect that we will find self-driving cars are too hard to put into the mix with human drivers and pedestrians. So we shall build / cordon off roads and end up with railways without rails.

Fascinated by the adelaide example - thank you

[tpmx]

Yeah, the amount of metro/central land railroads use is surprisingly huge.

[fomine3]

Airport is NIMBY

[908B64B197]

If they use them to fly to and from tiny airports they might fly only a few times per day with enough time to recharge in-between (because there's no demand).

Since the planes themselves are really small, they also won't spend a long time at the gate so they could be transported to a maintenance hangar to recharge.

[mapt]

Small-market, heavily subsidized short-haul segments fly half empty, and have a low flight cadence.

[legitster]

I think that the turnaround time is less important for the really small jets they are considering.

[mbreese]

I think it’s more important. A wide body long-haul plane takes a significant amount of time to turn around w.r.t. many other aspects — more passengers, cargo/luggage, fuel, food, etc. the bigger the plane, the longer this takes. I’ve been on small commuter planes that turn around in 20-30 min, landing to take off. These are the planes that turn around quickly as there are fewer passengers, they carry less baggage, and you don’t always need to refuel.

If anything, these shorter routes are more time-sensitive.

[wtvanhest]

That seems like an important question. Maybe they will have a lot of individual batteries that they can charge simultaneously.

Alternatively, maybe they could swap out the bottom of the fuselage or wings.

[NickM]

Even if they don't have super fast chargers or battery swaps, I'd imagine the cost of longer turn times might be offset by the substantially lower fuel costs.

[Hypx_]

Electric airplanes are increasingly just gadgetbahns of the sky. None of the are even remotely feasible, and reading the comments here it's clear that even if they did exist they'd be immediately disrupted by existing airplanes. I think it's time we stop giving them any more thought as they simply cannot work.